多维数据模型:
数据仓库和OLTP基于多维数据模型,该模型将数据看成数据立方体(data cube).
多维数据模型的形式有:
星型模式: 一个事实表,若干维度表
雪花模式:一个事实表,若干维度表,但是维度表是规范化的,即进一步把数据分解到附加的表中。省空间,花时间。
事实星座模式:多个事实表,它们各自可以有自己独有的维度表,也可以共享维度表,并且维度表可以是规范化的也可以不是规范化的。
数据挖掘查询语言DMQL:
用DMQL来定义数据立方体:
define cube <cube_name> [<dimension_list>]:<measure_list>
用DMQL来定义维度:
define dimension <dimension_name> as (<attribute_or_subdimentiosn_list>)
其中的黑体为关键字
用DMQL定义星型模型:
define cube sales star [time, item, branch, location]:dollars sold = sum(sales in dollars), units sold = count(*)
define dimension time as (time key, day, day of week, month, quarter, year)
define dimension item as (item key, item name, brand, type, supplier type)
define dimension branch as (branch key, branch name, branch type)
define dimension location as (location key, street, city, province or state,country)
用DMQL定义雪花模型:
define cube sales snowflake [time, item, branch, location]:dollars sold = sum(sales in dollars), units sold = count(*)
define dimension time as (time key, day, day of week, month, quarter, year)
define dimension item as (item key, item name, brand, type, supplier(supplier key, supplier type))
define dimension branch as (branch key, branch name, branch type)
define dimension location as (location key, street, city(city key, city, province or state, country)
用DMQL(Data Mining Query Language)定义星座模型:
define cube sales [time, item, branch, location]:dollars sold = sum(sales in dollars), units sold = count(*)
define dimension time as (time key, day, day of week, month, quarter, year)
define dimension item as (item key, item name, brand, type, supplier type)
define dimension branch as (branch key, branch name, branch type)
define dimension location as (location key, street, city, province or state, country)
define cube shipping [time, item, shipper, from location, to location]:dollars cost = sum(cost in dollars), units shipped = count(*)
define dimension time as time in cube sales
define dimension item as item in cube sales
define dimension shipper as (shipper key, shipper name, location as location in cube sales, shipper type)
define dimension from location as location in cube sales
define dimension to location as location in cube sales
概念分层(concept hierarchy):
(a)属性location的层次结构(a hierarchy for location)
(b)属性time的格(a lattice for time)
如果属性的值为连续值,那么将其离散化后也可以形成concept hierarchy.
OLAP:
上卷roll-up, 下钻drill-down, 切片slice, 切块dice,旋转 pivot